The present invention is applicable in fluid circuits such as those used in heat pump circuitry and may be used for the purpose of controlling the rate of fluid flow within the circuit in both one direction or in the opposed direction. In heat pump designs, the fluid circuit is designed to provide for cooling when the flow is in a specific direction within the circuit. If the flow within the circuit is reversed, the heat pump design will provide heating. It is well known that in heat pump operations, heat will move from a higher temperature to a lower temperature. Thus, if a heat transfer coil is kept at a lower temperature than its surroundings, it will pickup heat. Conversely, if the transfer coil is kept at higher temperature than its surroundings, it will give off heat. In the operation of a heat pump, in the cooling mode, cool refrigerant is passed through an indoor coil to accept heated ambient air from within a structure. The heated refrigerant is then run through a compressor to an outdoor coil wherein the heat is transferred outdoors. If the flow is reversed, a structure can be heated by having the refrigerant in an outdoor coil cooled sufficiently to draw heat from the outdoor ambient air which is then compressed and transferred to the indoor coil and then transferred as heat within the structure.
The flow of the refrigerant through the circuitry of the pump is usually controlled by a capillary tube device or a restrictor taken in combination with a capillary tube device. The capillary tubes are used to reduce pressure on the refrigerant therefore reducing the temperature of the refrigerant. Typically with capillary tube assemblies, there are two different capillary tubes and one or, more likely, two check valves that operate to route the refrigerant through one capillary tube for cooling and through the other capillary tube for heating. The use of such capillary tubes with or without a restrictor provides a continual source of problems in heat pump designs. The capillary tubes with their concomitant check valves and manifolds require at least six to seven different joints which must be brazed for installation. Each given joint provides a potential leak path for refrigerant thus providing a potential problem area. Further, the incorporation of the capillary tubes and/or restrictor combination is complicated in the design of heat pumps and many times internal filter screens are necessary to filter the refrigerant. The addition of such screens adds more complexity to the design of the heat pump.
Therefore, it is an object of the invention to provide a flow control mechanism which eliminates the complexities in design of the heat pump.
It is another object of the invention to minimize the number of braze joints within a heat pump circuit to thereby eliminate potential leak paths.
Finally, it is an object of the invention to provide precise metered flow for both the heating circuit and the cooling circuit of a heat pump.